Recent ESA/ESOC patents

The Advanced Operations Technologies Group at ESOC has filed five patents since 2009 in the areas of housekeeping data mining and compression. This page gives a brief oversight of each invention.

DrMUST: Automating the first steps of anomaly investigation

Once engineers have realised that an anomaly has happened, they face the problem of identifying the possible causes and other effects of the anomaly. DrMUST performs pattern matching to find similar behaviours across history (years) and correlation analysis to determine which other parameters (out of 20 000) are involved in a given anomaly. DrMUST can be used not only for anomaly investigation but also to perform characterisations.

DrMUST is used by several missions both for pattern matching and correlation analysis. Flight Control Teams report 20-30% effort reduction in performing anomaly investigation (the other 70-80% effort is taken up by taking corrective and preventive actions such as modifying procedures).

DrMUST uses speech recognition techniques to find similar patterns in order to cope with small deviations in system behaviour (in the same sense that the same word is spoken differently by two different speakers). Regarding correlation analysis, we have developed a robust technique that finds which parameters are somehow involved in a specific situation (e.g. anomaly, characterisation). The ESA Patent Group has decided to protect DrMUST by filing a patent application in the European Patent Office.

Novelty detection: A new telemetry monitoring paradigm

Being able to quickly identify anomalous behaviour allows reduction of downtime and optimum maintenance of spacecraft health.

The current approach built in our Mission Control System is to use out-of-limit checks. However, many behaviours are anomalous even if they are within limits. Novelty detection is a new monitoring paradigm that allows teams to detect unusual behaviours in telemetry parameters. An unusual behaviour is usually a signature of an anomaly. The novel detection monitoring approach requires very little engineering knowledge as it learns from given examples of nominal behaviour. It also produces few false alarms and is complementary to the existing out-of-limit paradigm.

The Novelty Detector has been validated with Venus Express, XMM and CryoSat-2. The Novelty Detector managed to detect the anomaly long before the out-of-limits checks did. In some cases, these anomalies were not even detected by the out-of-limits check. Flight control engineers check the Novelty Detection results daily as part of their monitoring tasks.

The monitoring technique based on Novelty Detection uses outlier detection techniques based on density. The assumption is that a new behaviour is often the signature of an anomaly. The ESA Patent Group has decided to protect the novelty detection-based monitoring technique by filing an international patent application.

Fractal resampling: Enhancing observability on ground for the same or even less bandwidth

On-board observability depends on the sampling rate used to perform on-board measurements. The fractal resampling technique allows high sampling on board while sending very little data, which can account for the most interesting information. This separation between data and information allows gaining on-board observability while reducing bandwidth requirements. The fractal resampling technique is currently used to enable data plotting for online applications.

Fractal resampling has been prototyped to demonstrate its feasibility. At the moment it is being used as a lossy compression technique to enable web plotting clients.

Fractal Resampling technology takes inspiration from the way 3D fractal terrain is generated in video games. We reverse the process starting with a given time series (e.g. in fractal terrain terms, the time series is the 'mountain'). The ESA Patent Group has decided to protect the fractal resampling technique by filing a patent application in the European Patent Office.

POCKET Compression: How to get ten times more information in your real-time data stream with minimal changes

One way of estimating the information content of a message is to compress it. Since, the information content of housekeeping telemetry packets is quite low, when they are stored in files they compress extremely well. Compressing packets and sending more of them in the same bandwidth would improve the information content of the data stream. This would bring benefits in terms of better reaction times and better spacecraft observability as well as reducing the upfront engineering effort and operations costs.

Most methods proposed for compressing housekeeping data only work on data that has been stored on board, usually in files. This requires major changes in on-board architecture. It also means that engineering work when designing packets/downlink schemes for packets that have to be sent in real-time still has to be done. This reduces the potential impact.

POCKET is a method for compressing packets in real-time, i.e. each individual packet is compressed into an equivalent smaller packet as soon as it is generated. The smaller packet can then be sent in realtime or stored for later transmission. This opens up the possibility of increasing the information content of both the playback and realtime telemetry streams with a single, unique process at generation time.

Note that no major changes in on-board architecture are required to implement it. POCKET is a software plug-in that is added just after each packet is generated. The input and output are packets and so all normal operations concepts can be applied. Another software plug-in is added just before the mission control system which intercepts the compressed packets and expands them before injection. The disturbance is minimal.

POCKET has been tested using real spacecraft housekeeping data and was found to compress significantly better than ZIP and significantly faster. Average compression ratios of 3 to 20 have been achieved depending on the mission. POCKET has been implemented in on-board software using the strictest space-coding standards and then prototyped and validated on an end-to-end system using real space hardware and a real mission compression system.

The results are very impressive. POCKET has been selected to fly on the ESA missions Proba-3 and OPS-SAT. It is also being considered for the TIA mission, Electra. Finally, it has been spun out for use in a UAV control system.

It is commonly believed that HKTM packets do not compress well. However, we have developed a lossless compression technique that provides massive data reduction. It is so simple that it can be implemented on board. The packet reader compression technique groups packet of the same type and reads them using the binary transposed feed, which experiences far less transitions than the traditional feed. This allows use of very simple and efficient compression algorithms (e.g. Run Length Encoding).

The packet reader compression technique has been validated on ground with satisfactory results (e.g. only 14% of data needed for all HKTM Rosetta packets). It has been prototyped and validated on on-board hardware (LEON2 processor). The packet reader compression technique has been identified as enabling technology for the Mars atmospheric sample return mission.

The ESA Patent Group has decided to protect the Packet Reader Compression technique by filing a patent application in the United States Patent and Trademark Office.